The use of various control arms and tension control mechanisms is quite well known for a number of applications. These devices are generally employed in order to control the speed of supply of various materials and/or to act as a take-up mechanism when slack develops between various processing stations and the like. The particular environments in which these devices may be used are quite numerous, as are the variety of these devices which are so employed.
As an example of such a tensioning and control system is that shown in U.S. Pat. No. 1,343,910 to Evans. In this patent a rheostat is controlled by the speed with which the supply strip is drawn into the processing station, and the rheostat in turn controls the speed at which the supply strip is unwound from its feed station. In addition, the initial activation of the rheostat is in turn controlled by the spring mechanisms 8 and 9 shown therein.
A similar type of speed control and tension mechanism is shown in U.S. Pat. No. 3,667,664 to Schroeder. In this mechanism deflection of a lever 6 caused by alterations in the tension in the supply strip is used to actuate a drive motor for the feed rollers. In particular, a potentiometer 22 can be employed to provide a signal for motor speed control purposes. Similar such devices are also shown in U.S. Pat. No. 2,474,620 to Fath, U.S. Pat. No. 2,345,765 to Michel, and U.S. Pat. No. 3,807,613 to Holm.
While a number of these devices also effect uniform tensioning of the continuous supply strip, there are also several other types of devices which have been utilized exclusively for such purposes. These include devices such as those shown in U.S. Pat. No. 3,826,442 to Bethke, in which the tension in an envelope machine for continuously supplying web material is sensed between a pair of rollers 46 and 48, and by means of a tension sensing roll 50, which pivots in response thereto so as to maintain uniform tension in the web. In addition, U.S. Pat. No. 1,158,432 to Benoit discloses a system for uniform tensioning in winding machines which employs a lever 18 pivoted about a bracket 26 and in which there are springs located between the lever and the bracket as well as on drum 26 to the roll 16 about which the thread being fed in that case is wound.
One specific environment, however, which raises particularly troublesome problems with respect to both tensioning and speed control is that where a continuous web is being fed to or from a processing station which effects an intermittent interruption of the feed thereto, such as various punch presses and the like. One mechanism which is employed in this general type of environment is that of U.S. Pat. No. 3,904,145 to Steinberger et al, which however relates to a copying machine in which the motor for the take-up reel 18 is controlled by means of braking of the supply strip between rollers 14 and 17.
In such an environment, where the continuous strip of material such as a metallic strip is being fed to or rereeled from such an apparatus, the strip is subject to violent initiation and termination of motion, on a continuous basis. At the same time, this same material is normally being continuously fed from a feed source, and/or being continuously rereeled onto a take-up reel. In order to operate in connection with such punch presses and like it is therefore necessary that a minimum degree of tension be applied to the strip in a reverse direction, i.e., so as to prevent perfect feeding and registration of the strip in the processing station where that is required. On the other hand, if there is too little tension on the strip problems of over-feeding may generally occur, with similar negative results.
In such environments single arm bars and the like, similar to those shown in some of the references discussed above, have generally been employed. These, however, are unsatisfactory in that they directly translate these changes in tension in the supply strip into changes in the speed of the unreeling or rereeling mechanism, which then occur far too rapidly. This generally results in excessive tension being imparted to the supply strip. Furthermore, because continuous cycling of the motor driving the unreeling or rereeling mechanism then occurs, large amounts of power are necessary in order to obtain such rapid acceleration and deceleration thereof, and the drive mechanism itself can become damaged or destroyed.